The present invention relates generally to an apparatus for the production of mixed gases. More particularly, the present invention relates to an improved apparatus for mixing two or more gases to a desired gas concentration.
Various devices have been available for years for gas mixing purposes, such as systems to be used in mixed-gas diving. Mixed-gas diving has increased in popularity over recent years as a way to limit common injuries sustained by self-contained underwater breathing apparatus (SCUBA) diving activities. Mixed gases have also been used in surface supplied diving and re-breather diving activities. Decompression sickness, commonly referred to as the xe2x80x9cbendsxe2x80x9d is a serious medical condition that can be experienced by divers that are exposed to elevated nitrogen levels forming in the bloodstream as the diver ascends from the increased pressure experienced at deeper depths. The nitrogen level formed in a diver""s bloodstream is a direct result of the amount of nitrogen in the air stored in a diver""s tanks and breathed at depth. Based on the understanding that the use of air having reduced amounts of nitrogen decreases the occurrence and seriousness of the bends in divers, the National Oceanographic and Atmospheric Association (NOAA) began experimenting with gases labeled xe2x80x9cNitroxxe2x80x9d that had reduced levels of nitrogen through the use of supplemental oxygen added to ambient air (Nitrox was first used by the British military in World War II, but NOAA began the first commercial experimentation). While ambient atmospheric air typically has approximately 21% oxygen concentration at sea level and a corresponding 79% nitrogen concentration, Nitrox was primarily developed to contain 32%-36% oxygen, having correspondingly decreased levels of nitrogen. These Nitrox gases that had reduced levels of nitrogen were found to reduce the occurrence and seriousness of divers contracting the bends, while minimizing oxygen toxicity problems. Further Nitrox research resulted in Nitrox blends ranging from 21% to 100% oxygen, depending on the desired use of the mixture and the equipment involved in production of the mixture. With the raised popularity of using Nitrox for recreational and commercial diving, further research led to the development of gases known as Trimix, a mixture of helium, oxygen, and nitrogen gas, which is also used for diving. However, Nitrox is currently the gas mixture of choice for the recreational diver.
The use of Nitrox gases for diving has increased dramatically and likewise has created a great demand in recreational and commercial diving operations for the production of Nitrox gas. Various prior art devices have attempted to address the mixing of gases for Nitrox and other gas production purposes, yet these devices have various shortcomings that are overcome by the present invention.
U.S. Pat. No. 4,860,803 to Wells teaches the use of a pressure regulator to control the injection of oxygen into a stream of ambient air in order to produce an oxygen enriched air mixture. This mixture is then compressed and delivered to storage or SCUBA cylinders for use in diving or other applications. Wells discloses a purely mechanical system, with no computer or monitoring control, thus requiring an operator to continuously observe the oxygen analyzer in order to provide the control element. Additionally, the location of the oxygen analyzer at the discharge side of the compressor system results in a large lag time of several minutes between the time adjustment is made to the oxygen concentration and when the results of that adjustment can be observed, leading to concentration maintenance difficulties. Wells also requires a source of oxygen appropriate for injection into the ambient air stream thus producing the chance of explosions and other inherent problems associated with the use of oxygen.
U.S. Pat. No. 5,992,464 to Cowell discloses a pre-compression Nitrox in-line blender that uses pressure adjusted by a regulator applied across an orifice to control the amount of oxygen added to ambient air. In Cowell, an oxygen analyzer is observed by the operator in order to provide the operator with information to make adjustments to maintain the desired output concentration. Similar to Wells, there is no computer control or monitoring systems thus requiring an operator to continuously observe the oxygen analyzer in order to provide the control element. The Cowell device also has inherent accuracy and safety problems should the operator be the least inattentive.
U.S. Pat. No. 5,915,834 to McCulloh discloses an apparatus for mixing two gases by using a source of forced or pressurized air and a pressurized source of oxygen flowing through regulators in order to supply a control valve entering into a mixing plenum. The shuttling between air and oxygen and the non-proportional nature of the mixing valve apparently renders the machine incapable of supplying a flow suitable for use with a positive displacement continuous flow machine such as a compressor. Additionally, the flow valve as described in McCulloh produces inherent overheating and life cycle limitations if operated in the disclosed manner.
The apparatus of the present invention overcomes many of the problems as found in prior art gas mixing devices by incorporating an input device for receiving desired mixed gas concentration data from the user along with a plurality of gas inlets through which a plurality of gases enter a homogenizing chamber for mixing of the plurality of gases into a mixed gas. One or more gas sensors read the concentration of the mixed gas and generate an output signal representative thereof, sending the output signal to a manager that then compares the output signal with the desired gas concentration data from the user and in turn generates a gas inlet signal to modify the flow of gas to maintain the desired mixed gas concentration.
In accordance with the present invention, an improved automatic gas blender is provided for automatically mixing two or more gases to a desired gas concentration. The automatic gas blender has an input device for receiving predetermined mixed gas concentration data from the user, such as the level of oxygen desired in a Nitrox mixture of the preferred embodiment. The automatic gas blender further comprises a plurality of gas inlet valves which allow a plurality of gas flows, such as ambient air and oxygen in the preferred embodiment for production of Nitrox gas mixture, to enter a homogenizing chamber where the plurality of gas flows are mixed into a mixed gas through the use of a series of mixing baffles. At least one gas sensor is provided for detecting the concentration of one or more components of the mixed gas and generating at least one output signal representative thereof. A manager is also provided for receiving the at least one output signal and comparing the at least one output signal with the predetermined mixed gas concentration data and in response generating a signal to at least one gas inlet valve to modify the plurality of gas flows to maintain the predetermined mixed gas concentration. Once the predetermined gas concentration is mixed and maintained, the mixed gas exiting the automatic gas blender can be compressed and transferred to high-pressure storage tanks.
In a preferred embodiment of producing a precise mixture of Nitrox (oxygen and ambient air), the user will enter the predetermined oxygen content for the Nitrox mixture into an input device, a preferred concentration of oxygen being between 21% and 40%. A fluid stream of ambient air will then pass through an air inlet valve into the gas addition area while a fluid stream of oxygen will pass through an oxygen inlet valve into the gas addition area. The two gas streams will merge and enter the homogenizing chamber where they will mix by passing across, around, or through at least one mixing baffle. An oxygen sensor will then measure the oxygen concentration of the mixed gas and generate an output signal representative thereof that is sent to the manager. The manager will receive the output signal and compare the signal with the predetermined oxygen content as entered by the user. The manager will then generate an oxygen inlet valve signal that is sent to the oxygen inlet valve in order to modify the valve setting, thus modifying the fluid stream of oxygen entering the gas addition area. This process is repeated until the predetermined oxygen content is reached, upon which time the gas is compressed and transferred to high-pressure storage tanks.
Therefore, it is an object of the present invention to provide a system for automatically blending two or more gases.
It is another object of the present invention to provide a system and method for automatically blending two or more gases to provide a breathing gas mixture for divers that significantly extends bottom time, reduces required decompression, and provides numerous physiologic and other benefits.
Yet another object of the present invention is to provide a method for producing a gas mixture, which can be made into a breathing quality gas mixture, that safely, automatically, accurately, and rapidly combines ambient air and pure oxygen to create a final mixture of a predetermined concentration.
Some of the objects of the invention having been stated hereinabove, other objects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.